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Comparing jsr166/src/main/java/util/PriorityQueue.java (file contents):
Revision 1.4 by tim, Mon May 19 02:45:07 2003 UTC vs.
Revision 1.25 by tim, Wed Aug 6 18:42:49 2003 UTC

#	Line 1 | Line 1
1		package java.util;
2
3	–	/*
4	–	* Todo
5	–	*
6	–	*   1) Make it serializable.
7	–	*/
8	–
3		/**
4	<	* An unbounded priority queue based on a priority heap.  This queue orders
5	<	* elements according to the order specified at creation time.  This order is
6	<	* specified as for {@link TreeSet} and {@link TreeMap}: Elements are ordered
4	>	* An unbounded priority {@linkplain Queue queue} based on a priority heap.
5	>	* This queue orders
6	>	* elements according to an order specified at construction time, which is
7	>	* specified in the same manner as {@link java.util.TreeSet} and
8	>	* {@link java.util.TreeMap}: elements are ordered
9		* either according to their <i>natural order</i> (see {@link Comparable}), or
10	<	* according to a {@link Comparator}, depending on which constructor is used.
11	<	* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the
12	<	* minimal element with respect to the specified ordering.  If multiple
13	<	* these elements are tied for least value, no guarantees are made as to
14	<	* which of elements is returned.
10	>	* according to a {@link java.util.Comparator}, depending on which
11	>	* constructor is used.
12	>	* <p>The <em>head</em> of this queue is the <em>least</em> element with
13	>	* respect to the specified ordering.
14	>	* If multiple elements are tied for least value, the
15	>	* head is one of those elements. A priority queue does not permit
16	>	* <tt>null</tt> elements.
17	>	*
18	>	* <p>The {@link #remove()} and {@link #poll()} methods remove and
19	>	* return the head of the queue.
20		*
21	<	* <p>Each priority queue has a <i>capacity</i>.  The capacity is the size of
22	<	* the array used to store the elements on the queue.  It is always at least
22	<	* as large as the queue size.  As elements are added to a priority list,
23	<	* its capacity grows automatically.  The details of the growth policy are not
24	<	* specified.
21	>	* <p>The {@link #element()} and {@link #peek()} methods return, but do
22	>	* not delete, the head of the queue.
23		*
24	<	*<p>Implementation note: this implementation provides O(log(n)) time for
25	<	* the <tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>
26	<	* methods; linear time for the <tt>remove(Object)</tt> and
27	<	* <tt>contains</tt> methods; and constant time for the <tt>peek</tt>,
28	<	* <tt>element</tt>, and <tt>size</tt> methods.
24	>	* <p>A priority queue has a <i>capacity</i>.  The capacity is the
25	>	* size of the array used internally to store the elements on the
26	>	* queue.
27	>	* It is always at least as large as the queue size.  As
28	>	* elements are added to a priority queue, its capacity grows
29	>	* automatically.  The details of the growth policy are not specified.
30	>	*
31	>	* <p>Implementation note: this implementation provides O(log(n)) time
32	>	* for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
33	>	* <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
34	>	* <tt>remove(Object)</tt> and <tt>contains(Object)</tt> methods; and
35	>	* constant time for the retrieval methods (<tt>peek</tt>,
36	>	* <tt>element</tt>, and <tt>size</tt>).
37		*
38		* <p>This class is a member of the
39		* <a href="{@docRoot}/../guide/collections/index.html">
40		* Java Collections Framework</a>.
41	+	* @since 1.5
42	+	* @author Josh Bloch
43		*/
44		public class PriorityQueue<E> extends AbstractQueue<E>
45	<	implements Queue<E>
46	<	{
45	>	implements Queue<E>, java.io.Serializable {
46	>
47		private static final int DEFAULT_INITIAL_CAPACITY = 11;
48
49		/**
50		* Priority queue represented as a balanced binary heap: the two children
51		* of queue[n] are queue[2*n] and queue[2*n + 1].  The priority queue is
52		* ordered by comparator, or by the elements' natural ordering, if
53	<	* comparator is null:  For each node n in the heap, and each descendant
54	<	* of n, d, n <= d.
53	>	* comparator is null:  For each node n in the heap and each descendant d
54	>	* of n, n <= d.
55		*
56	<	* The element with the lowest value is in queue[1] (assuming the queue is
57	<	* nonempty). A one-based array is used in preference to the traditional
58	<	* zero-based array to simplify parent and child calculations.
56	>	* The element with the lowest value is in queue[1], assuming the queue is
57	>	* nonempty.  (A one-based array is used in preference to the traditional
58	>	* zero-based array to simplify parent and child calculations.)
59		*
60		* queue.length must be >= 2, even if size == 0.
61		*/
62	<	private E[] queue;
62	>	private transient Object[] queue;
63
64		/**
65		* The number of elements in the priority queue.
#	Line 62 | Line 70 | public class PriorityQueue<E> extends Ab
70		* The comparator, or null if priority queue uses elements'
71		* natural ordering.
72		*/
73	<	private final Comparator<E> comparator;
73	>	private final Comparator<? super E> comparator;
74
75		/**
76		* The number of times this priority queue has been
77		* <i>structurally modified</i>.  See AbstractList for gory details.
78		*/
79	<	private int modCount = 0;
79	>	private transient int modCount = 0;
80
81		/**
82	<	* Create a new priority queue with the default initial capacity (11)
83	<	* that orders its elements according to their natural ordering.
82	>	* Creates a <tt>PriorityQueue</tt> with the default initial capacity
83	>	* (11) that orders its elements according to their natural
84	>	* ordering (using <tt>Comparable</tt>).
85		*/
86		public PriorityQueue() {
87	<	this(DEFAULT_INITIAL_CAPACITY);
87	>	this(DEFAULT_INITIAL_CAPACITY, null);
88		}
89
90		/**
91	<	* Create a new priority queue with the specified initial capacity
92	<	* that orders its elements according to their natural ordering.
91	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
92	>	* that orders its elements according to their natural ordering
93	>	* (using <tt>Comparable</tt>).
94		*
95		* @param initialCapacity the initial capacity for this priority queue.
96	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
97	+	* than 1
98		*/
99		public PriorityQueue(int initialCapacity) {
100		this(initialCapacity, null);
101		}
102
103		/**
104	<	* Create a new priority queue with the specified initial capacity (11)
104	>	* Creates a <tt>PriorityQueue</tt> with the specified initial capacity
105		* that orders its elements according to the specified comparator.
106		*
107		* @param initialCapacity the initial capacity for this priority queue.
108		* @param comparator the comparator used to order this priority queue.
109	+	* If <tt>null</tt> then the order depends on the elements' natural
110	+	* ordering.
111	+	* @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
112	+	* than 1
113		*/
114	<	public PriorityQueue(int initialCapacity, Comparator<E> comparator) {
114	>	public PriorityQueue(int initialCapacity,
115	>	Comparator<? super E> comparator) {
116		if (initialCapacity < 1)
117	<	initialCapacity = 1;
118	<	queue = new E[initialCapacity + 1];
117	>	throw new IllegalArgumentException();
118	>	this.queue = new Object[initialCapacity + 1];
119		this.comparator = comparator;
120		}
121
122		/**
123	<	* Create a new priority queue containing the elements in the specified
124	<	* collection.  The priority queue has an initial capacity of 110% of the
108	<	* size of the specified collection. If the specified collection
109	<	* implements the {@link Sorted} interface, the priority queue will be
110	<	* sorted according to the same comparator, or according to its elements'
111	<	* natural order if the collection is sorted according to its elements'
112	<	* natural order.  If the specified collection does not implement the
113	<	* <tt>Sorted</tt> interface, the priority queue is ordered according to
114	<	* its elements' natural order.
115	<	*
116	<	* @param initialElements the collection whose elements are to be placed
117	<	*        into this priority queue.
118	<	* @throws ClassCastException if elements of the specified collection
119	<	*         cannot be compared to one another according to the priority
120	<	*         queue's ordering.
121	<	* @throws NullPointerException if the specified collection or an
122	<	*         element of the specified collection is <tt>null</tt>.
123	>	* Common code to initialize underlying queue array across
124	>	* constructors below.
125		*/
126	<	public PriorityQueue(Collection<E> initialElements) {
127	<	int sz = initialElements.size();
126	>	private void initializeArray(Collection<? extends E> c) {
127	>	int sz = c.size();
128		int initialCapacity = (int)Math.min((sz * 110L) / 100,
129		Integer.MAX_VALUE - 1);
130		if (initialCapacity < 1)
131		initialCapacity = 1;
130	–	queue = new E[initialCapacity + 1];
132
133	<	if (initialElements instanceof Sorted) {
134	<	comparator = ((Sorted)initialElements).comparator();
135	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
136	<	queue[++size] = i.next();
137	<	} else {
133	>	this.queue = new Object[initialCapacity + 1];
134	>	}
135	>
136	>	/**
137	>	* Initially fill elements of the queue array under the
138	>	* knowledge that it is sorted or is another PQ, in which
139	>	* case we can just place the elements without fixups.
140	>	*/
141	>	private void fillFromSorted(Collection<? extends E> c) {
142	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
143	>	queue[++size] = i.next();
144	>	}
145	>
146	>
147	>	/**
148	>	* Initially fill elements of the queue array that is
149	>	* not to our knowledge sorted, so we must add them
150	>	* one by one.
151	>	*/
152	>	private void fillFromUnsorted(Collection<? extends E> c) {
153	>	for (Iterator<? extends E> i = c.iterator(); i.hasNext(); )
154	>	add(i.next());
155	>	}
156	>
157	>	/**
158	>	* Creates a <tt>PriorityQueue</tt> containing the elements in the
159	>	* specified collection.  The priority queue has an initial
160	>	* capacity of 110% of the size of the specified collection or 1
161	>	* if the collection is empty.  If the specified collection is an
162	>	* instance of a {@link java.util.SortedSet} or is another
163	>	* <tt>PriorityQueue</tt>, the priority queue will be sorted
164	>	* according to the same comparator, or according to its elements'
165	>	* natural order if the collection is sorted according to its
166	>	* elements' natural order.  Otherwise, the priority queue is
167	>	* ordered according to its elements' natural order.
168	>	*
169	>	* @param c the collection whose elements are to be placed
170	>	*        into this priority queue.
171	>	* @throws ClassCastException if elements of the specified collection
172	>	*         cannot be compared to one another according to the priority
173	>	*         queue's ordering.
174	>	* @throws NullPointerException if <tt>c</tt> or any element within it
175	>	* is <tt>null</tt>
176	>	*/
177	>	public PriorityQueue(Collection<? extends E> c) {
178	>	initializeArray(c);
179	>	if (c instanceof SortedSet<? extends E>) {
180	>	SortedSet<? extends E> s = (SortedSet<? extends E>) c;
181	>	comparator = (Comparator<? super E>)s.comparator();
182	>	fillFromSorted(s);
183	>	}
184	>	else if (c instanceof PriorityQueue<? extends E>) {
185	>	PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
186	>	comparator = (Comparator<? super E>)s.comparator();
187	>	fillFromSorted(s);
188	>	}
189	>	else {
190		comparator = null;
191	<	for (Iterator<E> i = initialElements.iterator(); i.hasNext(); )
139	<	add(i.next());
191	>	fillFromUnsorted(c);
192		}
193		}
194
195	+	/**
196	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
197	+	* specified collection.  The priority queue has an initial
198	+	* capacity of 110% of the size of the specified collection or 1
199	+	* if the collection is empty.  This priority queue will be sorted
200	+	* according to the same comparator as the given collection, or
201	+	* according to its elements' natural order if the collection is
202	+	* sorted according to its elements' natural order.
203	+	*
204	+	* @param c the collection whose elements are to be placed
205	+	*        into this priority queue.
206	+	* @throws ClassCastException if elements of the specified collection
207	+	*         cannot be compared to one another according to the priority
208	+	*         queue's ordering.
209	+	* @throws NullPointerException if <tt>c</tt> or any element within it
210	+	* is <tt>null</tt>
211	+	*/
212	+	public PriorityQueue(PriorityQueue<? extends E> c) {
213	+	initializeArray(c);
214	+	comparator = (Comparator<? super E>)c.comparator();
215	+	fillFromSorted(c);
216	+	}
217	+
218	+	/**
219	+	* Creates a <tt>PriorityQueue</tt> containing the elements in the
220	+	* specified collection.  The priority queue has an initial
221	+	* capacity of 110% of the size of the specified collection or 1
222	+	* if the collection is empty.  This priority queue will be sorted
223	+	* according to the same comparator as the given collection, or
224	+	* according to its elements' natural order if the collection is
225	+	* sorted according to its elements' natural order.
226	+	*
227	+	* @param c the collection whose elements are to be placed
228	+	*        into this priority queue.
229	+	* @throws ClassCastException if elements of the specified collection
230	+	*         cannot be compared to one another according to the priority
231	+	*         queue's ordering.
232	+	* @throws NullPointerException if <tt>c</tt> or any element within it
233	+	* is <tt>null</tt>
234	+	*/
235	+	public PriorityQueue(SortedSet<? extends E> c) {
236	+	initializeArray(c);
237	+	comparator = (Comparator<? super E>)c.comparator();
238	+	fillFromSorted(c);
239	+	}
240	+
241	+	/**
242	+	* Resize array, if necessary, to be able to hold given index
243	+	*/
244	+	private void grow(int index) {
245	+	int newlen = queue.length;
246	+	if (index < newlen) // don't need to grow
247	+	return;
248	+	if (index == Integer.MAX_VALUE)
249	+	throw new OutOfMemoryError();
250	+	while (newlen <= index) {
251	+	if (newlen >= Integer.MAX_VALUE / 2)  // avoid overflow
252	+	newlen = Integer.MAX_VALUE;
253	+	else
254	+	newlen <<= 2;
255	+	}
256	+	Object[] newQueue = new Object[newlen];
257	+	System.arraycopy(queue, 0, newQueue, 0, queue.length);
258	+	queue = newQueue;
259	+	}
260	+
261		// Queue Methods
262
263	+
264	+
265		/**
266	<	* Remove and return the minimal element from this priority queue if
147	<	* it contains one or more elements, otherwise <tt>null</tt>.  The term
148	<	* <i>minimal</i> is defined according to this priority queue's order.
266	>	* Add the specified element to this priority queue.
267		*
268	<	* @return the minimal element from this priority queue if it contains
269	<	*         one or more elements, otherwise <tt>null</tt>.
268	>	* @return <tt>true</tt>
269	>	* @throws ClassCastException if the specified element cannot be compared
270	>	* with elements currently in the priority queue according
271	>	* to the priority queue's ordering.
272	>	* @throws NullPointerException if the specified element is <tt>null</tt>.
273		*/
274	+	public boolean offer(E o) {
275	+	if (o == null)
276	+	throw new NullPointerException();
277	+	modCount++;
278	+	++size;
279	+
280	+	// Grow backing store if necessary
281	+	if (size >= queue.length)
282	+	grow(size);
283	+
284	+	queue[size] = o;
285	+	fixUp(size);
286	+	return true;
287	+	}
288	+
289		public E poll() {
290		if (size == 0)
291		return null;
292	<	return remove(1);
292	>	return (E) remove(1);
293		}
294
295	+	public E peek() {
296	+	return (E) queue[1];
297	+	}
298	+
299	+	// Collection Methods - the first two override to update docs
300	+
301		/**
302	<	* Return, but do not remove, the minimal element from the priority queue,
303	<	* or <tt>null</tt> if the queue is empty.  The term <i>minimal</i> is
304	<	* defined according to this priority queue's order.  This method returns
163	<	* the same object reference that would be returned by by the
164	<	* <tt>poll</tt> method.  The two methods differ in that this method
165	<	* does not remove the element from the priority queue.
302	>	* Adds the specified element to this queue.
303	>	* @return <tt>true</tt> (as per the general contract of
304	>	* <tt>Collection.add</tt>).
305		*
306	<	* @return the minimal element from this priority queue if it contains
307	<	*         one or more elements, otherwise <tt>null</tt>.
306	>	* @throws NullPointerException {@inheritDoc}
307	>	* @throws ClassCastException if the specified element cannot be compared
308	>	* with elements currently in the priority queue according
309	>	* to the priority queue's ordering.
310		*/
311	<	public E peek() {
312	<	return queue[1];
311	>	public boolean add(E o) {
312	>	return super.add(o);
313		}
314
315	<	// Collection Methods
175	<
315	>
316		/**
317	<	* Removes a single instance of the specified element from this priority
318	<	* queue, if it is present.  Returns true if this collection contained the
319	<	* specified element (or equivalently, if this collection changed as a
317	>	* Adds all of the elements in the specified collection to this queue.
318	>	* The behavior of this operation is undefined if
319	>	* the specified collection is modified while the operation is in
320	>	* progress.  (This implies that the behavior of this call is undefined if
321	>	* the specified collection is this queue, and this queue is nonempty.)
322	>	* <p>
323	>	* This implementation iterates over the specified collection, and adds
324	>	* each object returned by the iterator to this collection, in turn.
325	>	* @throws NullPointerException {@inheritDoc}
326	>	* @throws ClassCastException if any element cannot be compared
327	>	* with elements currently in the priority queue according
328	>	* to the priority queue's ordering.
329	>	*/
330	>	public boolean addAll(Collection<? extends E> c) {
331	>	return super.addAll(c);
332	>	}
333	>
334	>
335	>	/**
336	>	* Removes a single instance of the specified element from this
337	>	* queue, if it is present.  More formally,
338	>	* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
339	>	* o.equals(e))</tt>, if the queue contains one or more such
340	>	* elements.  Returns <tt>true</tt> if the queue contained the
341	>	* specified element (or equivalently, if the queue changed as a
342		* result of the call).
343		*
344	<	* @param o element to be removed from this collection, if present.
345	<	* @return <tt>true</tt> if this collection changed as a result of the
346	<	*         call
347	<	* @throws ClassCastException if the specified element cannot be compared
186	<	*            with elements currently in the priority queue according
187	<	*            to the priority queue's ordering.
188	<	* @throws NullPointerException if the specified element is null.
344	>	* <p>This implementation iterates over the queue looking for the
345	>	* specified element.  If it finds the element, it removes the element
346	>	* from the queue using the iterator's remove method.<p>
347	>	*
348		*/
349	<	public boolean remove(Object element) {
350	<	if (element == null)
351	<	throw new NullPointerException();
349	>	public boolean remove(Object o) {
350	>	if (o == null)
351	>	return false;
352
353		if (comparator == null) {
354		for (int i = 1; i <= size; i++) {
355	<	if (((Comparable)queue[i]).compareTo(element) == 0) {
355	>	if (((Comparable<E>)queue[i]).compareTo((E)o) == 0) {
356		remove(i);
357		return true;
358		}
359		}
360		} else {
361		for (int i = 1; i <= size; i++) {
362	<	if (comparator.compare(queue[i], (E) element) == 0) {
362	>	if (comparator.compare((E)queue[i], (E)o) == 0) {
363		remove(i);
364		return true;
365		}
#	Line 210 | Line 369 | public class PriorityQueue<E> extends Ab
369		}
370
371		/**
372	<	* Returns an iterator over the elements in this priority queue.  The
373	<	* first element returned by this iterator is the same element that
215	<	* would be returned by a call to <tt>peek</tt>.
372	>	* Returns an iterator over the elements in this queue. The iterator
373	>	* does not return the elements in any particular order.
374		*
375	<	* @return an <tt>Iterator</tt> over the elements in this priority queue.
375	>	* @return an iterator over the elements in this queue.
376		*/
377		public Iterator<E> iterator() {
378		return new Itr();
#	Line 225 | Line 383 | public class PriorityQueue<E> extends Ab
383		* Index (into queue array) of element to be returned by
384		* subsequent call to next.
385		*/
386	<	int cursor = 1;
386	>	private int cursor = 1;
387
388		/**
389		* Index of element returned by most recent call to next or
390		* previous.  Reset to 0 if this element is deleted by a call
391		* to remove.
392		*/
393	<	int lastRet = 0;
393	>	private int lastRet = 0;
394
395		/**
396		* The modCount value that the iterator believes that the backing
397		* List should have.  If this expectation is violated, the iterator
398		* has detected concurrent modification.
399		*/
400	<	int expectedModCount = modCount;
400	>	private int expectedModCount = modCount;
401
402		public boolean hasNext() {
403		return cursor <= size;
#	Line 249 | Line 407 | public class PriorityQueue<E> extends Ab
407		checkForComodification();
408		if (cursor > size)
409		throw new NoSuchElementException();
410	<	E result = queue[cursor];
410	>	E result = (E) queue[cursor];
411		lastRet = cursor++;
412		return result;
413		}
#	Line 272 | Line 430 | public class PriorityQueue<E> extends Ab
430		}
431		}
432
275	–	/**
276	–	* Returns the number of elements in this priority queue.
277	–	*
278	–	* @return the number of elements in this priority queue.
279	–	*/
433		public int size() {
434		return size;
435		}
436
437		/**
285	–	* Add the specified element to this priority queue.
286	–	*
287	–	* @param element the element to add.
288	–	* @return true
289	–	* @throws ClassCastException if the specified element cannot be compared
290	–	*            with elements currently in the priority queue according
291	–	*            to the priority queue's ordering.
292	–	* @throws NullPointerException if the specified element is null.
293	–	*/
294	–	public boolean offer(E element) {
295	–	if (element == null)
296	–	throw new NullPointerException();
297	–	modCount++;
298	–
299	–	// Grow backing store if necessary
300	–	if (++size == queue.length) {
301	–	E[] newQueue = new E[2 * queue.length];
302	–	System.arraycopy(queue, 0, newQueue, 0, size);
303	–	queue = newQueue;
304	–	}
305	–
306	–	queue[size] = element;
307	–	fixUp(size);
308	–	return true;
309	–	}
310	–
311	–	/**
438		* Remove all elements from the priority queue.
439		*/
440		public void clear() {
#	Line 332 | Line 458 | public class PriorityQueue<E> extends Ab
458		assert i <= size;
459		modCount++;
460
461	<	E result = queue[i];
461	>	E result = (E) queue[i];
462		queue[i] = queue[size];
463		queue[size--] = null;  // Drop extra ref to prevent memory leak
464		if (i <= size)
#	Line 353 | Line 479 | public class PriorityQueue<E> extends Ab
479		if (comparator == null) {
480		while (k > 1) {
481		int j = k >> 1;
482	<	if (((Comparable)queue[j]).compareTo(queue[k]) <= 0)
482	>	if (((Comparable<E>)queue[j]).compareTo((E)queue[k]) <= 0)
483		break;
484	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
484	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
485		k = j;
486		}
487		} else {
488		while (k > 1) {
489		int j = k >> 1;
490	<	if (comparator.compare(queue[j], queue[k]) <= 0)
490	>	if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
491		break;
492	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
492	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
493		k = j;
494		}
495		}
#	Line 382 | Line 508 | public class PriorityQueue<E> extends Ab
508		int j;
509		if (comparator == null) {
510		while ((j = k << 1) <= size) {
511	<	if (j<size && ((Comparable)queue[j]).compareTo(queue[j+1]) > 0)
511	>	if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
512		j++; // j indexes smallest kid
513	<	if (((Comparable)queue[k]).compareTo(queue[j]) <= 0)
513	>	if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
514		break;
515	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
515	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
516		k = j;
517		}
518		} else {
519		while ((j = k << 1) <= size) {
520	<	if (j < size && comparator.compare(queue[j], queue[j+1]) > 0)
520	>	if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
521		j++; // j indexes smallest kid
522	<	if (comparator.compare(queue[k], queue[j]) <= 0)
522	>	if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
523		break;
524	<	E tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
524	>	Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
525		k = j;
526		}
527		}
528		}
529
530	+
531		/**
532	<	* Returns the comparator associated with this priority queue, or
533	<	* <tt>null</tt> if it uses its elements' natural ordering.
532	>	* Returns the comparator used to order this collection, or <tt>null</tt>
533	>	* if this collection is sorted according to its elements natural ordering
534	>	* (using <tt>Comparable</tt>).
535		*
536	<	* @return the comparator associated with this priority queue, or
537	<	*         <tt>null</tt> if it uses its elements' natural ordering.
536	>	* @return the comparator used to order this collection, or <tt>null</tt>
537	>	* if this collection is sorted according to its elements natural ordering.
538		*/
539	<	Comparator<E> comparator() {
539	>	public Comparator<? super E> comparator() {
540		return comparator;
541		}
542	+
543	+	/**
544	+	* Save the state of the instance to a stream (that
545	+	* is, serialize it).
546	+	*
547	+	* @serialData The length of the array backing the instance is
548	+	* emitted (int), followed by all of its elements (each an
549	+	* <tt>Object</tt>) in the proper order.
550	+	* @param s the stream
551	+	*/
552	+	private void writeObject(java.io.ObjectOutputStream s)
553	+	throws java.io.IOException{
554	+	// Write out element count, and any hidden stuff
555	+	s.defaultWriteObject();
556	+
557	+	// Write out array length
558	+	s.writeInt(queue.length);
559	+
560	+	// Write out all elements in the proper order.
561	+	for (int i=0; i<size; i++)
562	+	s.writeObject(queue[i]);
563	+	}
564	+
565	+	/**
566	+	* Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
567	+	* deserialize it).
568	+	* @param s the stream
569	+	*/
570	+	private void readObject(java.io.ObjectInputStream s)
571	+	throws java.io.IOException, ClassNotFoundException {
572	+	// Read in size, and any hidden stuff
573	+	s.defaultReadObject();
574	+
575	+	// Read in array length and allocate array
576	+	int arrayLength = s.readInt();
577	+	queue = new Object[arrayLength];
578	+
579	+	// Read in all elements in the proper order.
580	+	for (int i=0; i<size; i++)
581	+	queue[i] = s.readObject();
582	+	}
583	+
584		}
585	+

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